Graphics are often produced by imaging plastic films using methods such as screen printing, cutting, electrostatic printing, or inkjet printing. These graphics are adhered to surfaces such as cars, buses, trucks, walls, billboards, etc. When plastic film is used for fleet decoration, it is typically applied over the rivets that are used to assemble the trailer or vehicle bodies. To provide a high quality graphic appearance, the film should be intimately adhered to the surface around the rivets. Because the rivets are raised from the surrounding surface, air is trapped under the film around each rivet. The air must be removed from the pocket around the rivet before the film can be completely adhered to the area around the rivet. Typically, the film is perforated using a single needle, often referred to as an air release tool. Often, four or more holes are made in the film immediately surrounding the rivet using the air release tool. This process is time consuming and physically demanding.
Multiple point pins have been developed that will punch multiple holes with a single application of pressure. The pins are arranged in a circular row around a central plunger that is free of pins. In some tools, the plunger may be spring-loaded such that it moves inwardly as pressure is applied to the tool. The plunger may also include a concave depression to facilitate alignment of the tool over a rivet. This tool may reduce the time for perforating the film around rivets as compared to a single-needled tool, but the pins must be carefully aligned such that no single pin strikes the head of the rivet or all the other pins will be prevented from making contact and perforating the film. In addition, these tools are relatively expensive to manufacture and, thus, are not widely available.
A similar tool is also available in which the pins are arranged in a circular row about the central plunger. Both the pins and the plunger are spring-loaded such that both the pins and the plunger can be depressed into the body of the tool. Because only a single circular row of pins is provided, however, alignment of the tool over the rivet is important to ensure proper removal of the air trapped around the rivet.
Other systems that have been considered are pounce wheels--wheels with a row of pins projecting from the outer surface of the wheel. Registration of these wheels is not required, but multiple passes are usually required to provide adequate placement of the holes. Using them typically results in additional unnecessary holes throughout the film because the user typically makes four or more straight rows of perforations around each rivet. Those additional perforations are not required to release the entrapped air, and may adversely affect the appearance and/or durability of the graphic.
In addition to pounce wheels with single rows of pins, multiple pounce wheels mounted on a single axle have been presented. When these devices are advanced over rivets, however, the pins surrounding the rivet are raised and do not form the perforations required to release entrapped air from around the rivet.